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Astroflight Challenger build

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Old 02-09-2016, 11:26 AM
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USSBB57
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Default Astroflight Challenger build

Day 1

I spent most of the day cleaning out the attic and setting up shop, then put in a couple hours building the basic fuselage.

Given the open frame wing, with sheeting only over the center section, there is not a lot of wood in the kit.



It's straight forward, build flat on the plan stuff. It uses a 1/16" crutch and 3/16" square stock to support the sides and the two formers. The front former is 1/8" lite ply and the rear former is 3/32" balsa. Cross grain 1/16" sheeting is then applied top and bottom, giving 1/8" total under the crutch on the fuse from the wing TE forward.





It only took a couple hours to get the basic structure completed.


Day 2

The original used an Astroflight 05 brushed motor, and I opted to use a Turnigy D3530/14 1100Kv motor, which is a little larger in diameter than the Astroflight motor. The first step was to use the drill press, milling vice and 1 1/2" hole saw to enlarge the hole in the nose block. I then inlet the block about 1/2" to bring the shorter out runner motor flush with the nose block

It was a big snug around the motor leads, so I added a little clearance.





I then fitted a 1/16" lite ply firewall to the back of the nose block, and then used a razor saw to cut the top of the firewall and the nose block down flush with the fuselage sides.




It took a couple hours to get the nose block properly aligned, with 6 degrees down thrust and 1 degree of right thrust, and add another 1/8 of cowl to fit the block to the spinner. I cut enough clearance for the shaft in the center of the cowl extension and then enlarged the hole after it was fitted, leaving about 3/32" wall thickness

I then enlarged the hole in the ply former to allow the 2200 mAh battery to fit through the former, to give me more latitude in adjusting the CG.

I also installed the rudder and elevator servos and made provisions for them to move back one servo length if needed, then test fit all the bits and pieces:



Then I test fit all the bits and pieces:

Turnigy 3530/14 11KV motor
30 amp ESC 3A UBEC speed control
2200 mAh 3S 30C battery
Turnigy 6 ch park flyer receiver
Turnigy TSS-10 HM, 10 gram/2.2 Kg servos



Then I fit the hatch and did some sanding of the nose block and hatch.





I sanded some more to lower the profile on the hatch after this picture was taken and got slightly cleaner lines, but its' still going to be a bit blunt compared to my spinner.

If I scratch build another one, I'll increase the taper on the fuselage sides to lower the top of the nose by about 1/4" as the height it has now isn't needed, and I round the nose block to more of an oval shape and bend the sides in slightly to meet it, to eliminate some of the boxy lines.

The fun part however was when I fired it up. With a 10-6 folding prop the static thrust was impressive, and with a 12-6 folding prop it was even more impressive, although I noted the spinner and prop started slowly walking forward off the shaft at full thrust. Obviously, the prop nut needs to be snugged down a bit more than I'd thought.

I need to get my Eagle Tree data logger and power panel rewired for XT60 connectors, then I'll see what it's drawing for amps.

Finally, I spent about an hour building and sanding the vertical fin, rudder and stabilizer and elevator, along with cutting the hinge slots. I used slightly larger stock for the rudder post but otherwise stayed with the plan.

The kit included flat stock for the elevator and I may substitute TE stock to reduce the sanding that will be needed to get the trailing edge thinned.

-----

I'm not sure yet on antenna orientation for the 2.4 Ghz receiver. It seems that the pair of antenna should be straight and at 90 degree angles to one another, so I suspect I'll route one fore or aft along the fuselage, and run the other out along the trailing edge of the wing. I'm open to suggestions...
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Old 02-10-2016, 02:12 AM
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USSBB57,
Very informative thread on this Astro Challenger build. I have a kit myself (somewhere in the shop rafters) but in the original geared motor drive version. This model specifies an geared Astro 05 Cobalt Motor (brushed) and an 12 x 6 folding prop. I recall that there were some wing incidence issues with this version but the direct drive version is OK.
I do have flying, a Larry Jolly "Electricus" with the Astro 05 Cobalt Motor and a Graupner 7.5 x 4 Folder Prop. This is very similar to your direct drive "Challenger" and you should be very pleased with the performance especially with the brushless motor and a 10 x 6. I'm running a 2S 2000 LiPo for the motor and a 35 A brushed ESC. All up weight is about 32 oz. Let us know how the flights turn out.

For your 2.4 Ghz antenna orientation, I suggest mounting them orthogonally aft of the wing trailing edge, like rabbit ears on old time TV. You can thread the antennas thru nyrod tubes and Spectrum even offers an 2.4 Ghz Antenna Exit Guide kit- SPM6824
Rgds,
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Old 02-25-2016, 04:34 PM
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paul_spiers
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I was given an Astro 05 cobalt motor with a gear box. I want to put in a Slow Poke airplane. It does not have an ESC. What will work for an ESC / Battery combination? Thanks, Paul
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Old 02-25-2016, 10:58 PM
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Paul,
You want to use a brushed ESC with your geared Astro 05 Cobalt Motor. The ESC should be at least 35 A size and compatible with a 2S LiPo ( or 7.4V battery). Your problem will be finding a brushed ESC as most modern ESC's are designed for brushless motors. I scoured the NEAT Fair, major E-flight event, for a brushed ESC with "No Joy". Finally bought one from a fellow club member who picked one up at a local swap meet. Astro once offered an electronic switch, essentially a relay, that would turn their motors on/off from the throttle port of your receiver, however there was no speed throttling capability with this switch. Good luck on what you find.
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